Acrylate, methacrylate and other unsaturated monomers are widely used in coatings, adhesives, sealants, and elastomers, and may be crosslinked by ultraviolet light radiation or peroxide initiated free radical cure. These are typically low molecular weight multifunctional compounds which may be volatile or readily absorbed through skin and can cause adverse health effects. Functionalized polymers may overcome some of these drawbacks; generally, polymers are nonvolatile compounds, not readily absorbed through skin. However, multistep syntheses may be required, low functionality may be detrimental to reactivity and final properties, and catalyst or initiator may be required to effect crosslinking.
The Michael addition of acetoacetate donor compounds to multiacrylate receptor compounds to make crosslinked polymers has been described in the literature. For example, Mozner and Rheinberger reported the Michael addition of acetoacetates having a .beta.-dicarbonyl group to triacrylates and tetracrylates. Macromolecular Rapid Communications 16 135-138 (1995). The products formed were crosslinked gels. In one of the reactions, Mozner added one mole of trimethylol propane triacrylate (TMPTA) having 3 functional groups to one mole of polyethylene glycol (600 molecular weight) diacetoacetate (PEG600-DAA) having two functional groups. (Each "acetoacetate functional group" reacts twice, thus each mole of diacetoacetate has four reactive equivalents.) ##STR1## Mole Ratio of TMPTA: PEG 600 DAA=1:1 Ratio of acrylate: acetoacetate functional groups=3:2
Ratio of reactive equivalents=3:4